1. Field of the Invention
This invention relates to printing systems particularly suited for printing multiple character languages such as Chinese and Japanese Kanji.
2. Summary of the Prior Art
Conventional printing systems such as typewriters and other word processing systems are usually designed for printing languages such as English that have a relatively small number of alphabetic characters which are combined to form words. Due to the large number of characters necessary to print multiple character languages such as Chinese, the keyboards and/or printing elements of these conventional systems are generally inadequate for printing languages in which one character represents one word. Chinese, for example, requires the use of at least about 2,500 characters, and up to about 10,000 characters if less frequent words and historic character forms are needed, while Japanese Kanji requires about 2,500 characters to print the language.
Consequently, the commonly used current Chinese typewriter is a device having individual lead character faces laid out in a flat bed matrix. The appropriate character face to be printed is visually located by the operator who then activates a stylus which mechanically lifts the character face for printing. When uncommon characters are required, they must be individually selected from a separate tray and placed in the bed for use. As a result, the character printing process is a time-consuming operation with character-printing speeds of about 10 or more characters per minute. Additionally, considerable time is required to train the operator to easily select the appropriate characters from the bed.
Various alternate printing systems have been developed to overcome some of the problems associated with the use of the traditional Chinese typewriter, and to develop word processing systems capable of encoding and storing as well as printing the characters. Some such systems have incorporated a separate visual character matrix in order to aid the operator in selecting the appropriate character. Other systems have utilized the above flat bed matrix system to create a word processing system capable of encoding and printing Chinese by generating and storing the X and Y coordinates of the desired characters in the matrix and using an automatic printer to print the encoded characters. Such a system is described in U.S. Pat. No. 4,064,983.
Some similar systems have been developed in which the character grid is wrapped around a rotating drum rather than laid out on a flat bed matrix. The drum is rotated for visual location of the desired characters by means of a cursor, and a switch is activated to encode the character coordinates. The above alternate systems frequently still present problems, however, in view of the difficulties associated with printing the characters at high speeds with high quality print. Additionally, complicated control mechanisms are frequently necessary, and inexpensive construction of the systems can be difficult.
A keyboard system has been developed for use in connection with a Chinese character teleprinter which utilizes a standard western keyboard for encoding characters and storing the codes with only two to three keyboard strokes per character. It is described in U.S. Pat. No. 3,809,204, and is disclosed in association with a visual character board displaying the characters in relation to the keys. The characters are coded by means of a 6 or 7 element code unit, two code units being used to describe each character. Each key on the keyboard can be used to independently produce a 6-element code unit, and the "shift keys" can be used when 7-element code units are to be used. As a result, only two keys need be depressed for production of a character when a 6-element code unit is used, and a maximum of three or four keystrokes are used when coding characters using 7-element code units. However, this keyboard system as disclosed is adapted for encoding and storing encoded characters and is not combined with a printing head for direct printing of the characters.
Additional Chinese typewriters more like standard western typewriters have been developed which divide the characters into zones. An individual character is built up by keyboard composition of its various zones before printing. However, this method frequently requires the operator to use an average of about 9 key strokes to print each character, and problems with the print head still exist.
Furthermore, a printer has been developed and is described in U.S. Pat. No. 4,026,403, which utilizes a group of circular print wheels with spokes extending from a central hub and a series of character faces circumferentially disposed at the periphery of the spokes. At given signals, the carriage which stores the print wheels below the platen revolves to place any selected print wheel in a pre-selected position from which the wheel is upwardly pivoted to a print position adjacent the platen. Subsequently, the print wheel is rotated for printing the selected peripheral character.
However, this printer, even when designed for use in printing only 2,000 to 2,500 characters, usually requires three mechanical steps to print a given character: rotation of the carriage, displacement of a print wheel over a distance in excess of the diameter of the wheel into print position, and rotation of the print wheel itself. Additionally, this printer requires a rather large number of print wheels, about 130 to over 200, to print about 10,000 characters if the wheels contain about 46 to 75 each as suggested, and the printer as disclosed has not been adapted for use with a specialized keyboarding system.